Electronic apparatus



358-190. (3R Z1235a659 5R March 18, 194-1. Q WHITE 2,235,659

ELECTRONIC APPARATUS Filed Oct. 5, 1938 I I 1 f ifgg V1050 AUDIO WU/TS RECEIVER 2505/1 52 HIGH VOLTAGE POWER SUPPLY a 7 5 Q ukfJW-M 1w; FRAME DEFLEC'T/NG J? 1/ DEFLECT/A/G co/zs cams INVENTOR Patented Mar. 18, 1941 NITED STATES PATENT OFFICE ELECTRONIC APPARATUS Application October 5, 1938, Serial No. 233,341 In Great Britain October 12, 1937 4 Claims.

This invention relates to cathode ray tube apparatus employing a cathode ray tube in which an electron gun provides a beam of electrons which is deflected over a fluorescent or other screen or target element within the tube.

It is desirable that in the undeflected position, the beam should impinge on the screen at its center in order that as much latitude for deflection in all directions may be allowed and the built-up picture in the case of a television receiving tube should be correctly centered. The mechanical disposition of the electron gun Within a cathode ray tube is such that when an electron beam is generated and is not subject to de fleeting forces it may impinge on the screen at an undesirable distance from the center.

In order to effect adjustment of the beam it has previously been proposed in the specification of British Patent #418,940 to connect a potentiometer across a source of high tension supply for the anodes of tubes in the deflecting circuit of a television receiver and to connect the electromagnetic deflecting coils of a cathode ray tube to an adjustable tapping point in said potentiometer. The adjustable direct current thus passed through the coils facilitates the deflection of the beam so that normally it impinges upon the center of the tube screen.

This method is particularly applicable to the case in which the deflecting coils are connected directly in the anode circuit of the output tube of the deflecting circuit. It is however often desirable to couple the output from the deflecting circuit to the deflecting coils by means of a transformer to give a voltage step-down and the method proposed in specification of British Patent #418,940 is not then applicable.

When a step-down coupling transformer is used the deflecting coils have fewer turns and a larger direct current is needed for centering of the cathode ray beam upon the screen or target. Such a current may be of the same order as the total or the greater part of the current in the high voltage circuit for a complete television receiver, and it is clearly uneconomical to make an additional demand on the high voltage supply to this extent. The voltage required is however quite low.

According to the present invention apparatus for effecting adjustment of a desired steady deflection of the electron beam in a cathode ray tube provided with electromagnetic deflecting coils comprises a source of high tension current supply connected with a load and means for passing an adjustable fraction of the high voltage current fed to said load through said coils for the purpose of applying a desired steady deflection to the electron beam. The load may be constituted by the scanning circuits or the sound or video receiving circuits in television apparatus or a combination of such circuits. The load current may be passed through a resistance across which a potentiometer is connected, tappings in said potentiometer being taken to said deflecting coils.

In order that the nature of the invention may be more clearly understood, a circuit arrangement embodying the invention will now be described by way of example in greater detail in connection with the accompanying drawing which shows one preferred form of arrangement for the circuit.

Referring now to the drawing, a source of high tension supply I is shown connected to the scanning or cathode ray beam deflecting circuits 2, the video or picture receiver 3 and sound or audio receiver 4 of suitable television receiving apparatus. A resistance 5 of the order of 10 to 50 ohms is connected in series with the negative terminal of the high voltage source of supply. The potential across the resistance 5 is smoothed by an inductance 6 and condensers l and 8 and applied to potentiometers 9 and Ill. Adjustable tappings in these potentiometers are connected directly with the frame deflecting coils II and the line deflecting coils l2 of a cathode ray tube (not shown by the drawing for simplification reasons) of the usual and well known type used in television receivers and described in many places in published literature.

It will be clear that by adjustment of the tappings in th potentiometers any desired steady direct current may be passed through either the line or frame deflecting coils for the purpose of controlling the steady position of the electron beam of the cathode ray tube and thus to insur initial centering.

While in the arrangement described, the centering current is taken from a resistance through which the total load current passes, it will be understood that it may not be necessary or desirable to use the total load current. Thus, the load current of one or more valves in the scanning circuits or the video or audio channels may be by-passed direct to the negative terminal instead of being allowed to flow through the resistance 5. The major portion of the load current is, however, in such a case available for the purpose of effecting a desired steady deflection in accordance with the invention.

Having now described the invention what is claimed is the following:

1. A television receiving system comprising a video receiver, an audio receiver for receiving sound signals accompanying video signals, a Video reproducer including a cathode ray tube and cathode ray deflecting means, a source of supply voltage, a series resistance connected in one lead of said source of voltage, means to supply voltage from said source to said video receiver, said audio receiver, and said deflecting means through said resistance, a potentiometer connected across said resistance and connections from said deflecting means to said potentiometer.

2. A television receiving system as claimed in claim 1, wherein said deflecting means comprises magnetic deflection coils and means to generate deflecting energy and connection from said means to generate deflecting energy to said magnetic coils.

3. A television receiving system as claimed in claim 1, and wherein aid deflecting means comprises magnetic deflection coils and means to generate deflecting energy and connection from said means to generate deflecting energy to said magnetic coils, and wherein the magnetic deflecting coils are connected to said potentiometer.

4. A television receiving system as claimed in claim 1, and wherein said potentiometer includes serially connected impedances and smoothing condensers.

ERIC LAWRENCE CASLING WHITE. 

